While the barbell squat may be considered the king of all exercises, it is hard not to consider the barbell deadlift of equal, if not greater importance. The deadlift targets many of the major muscle groups of the body in a very taxing way.
The primary targets of the deadlift are those muscles which compose the posterior chain. These include the hamstrings, glutes, and the spinal erectors. The quadriceps are also involved as the athlete extends the knee during the movement, although less force is placed through the knee joint compared to squatting exercises, hence the reduced stimulation of the knee extenders in comparison. Away from the lower body - the abdominals work to stabilise the trunk, and the muscles of the upper back act as stabilisers as the scapular retracts.
For bodybuilders and general gym-goers, the deadlift offers a way of taxing many muscle groups at once to induce hypertrophy (muscle growth), as well as improved overall strength. For athletes, the deadlift can be used to improve strength and power of the hip and knee extenders, which is readily transferable to many sporting and athletic actions.